v0.11.0: Plugin / Slot system

- defslot: register render functions into named slots with ordering
- slot-render: call all registered render-fns for a slot
- Slot modes designed (stack/replace/single-winner) but mode dispatch
  is implicit via the registration API
- slot-p, clear-slot, list-slots for lifecycle management
- Slots stored in a hash table keyed by string (equal test)
- 4 tests, 100% passing

org/slot.org

@@ -0,0 +1,97 @@
+#+TITLE: Plugin / Slot System (v0.11.0)
+#+DATE: 2026-05-11
+#+AUTHOR: Amr Gharbeia / Hermes
+
+* Overview
+
+Extensible named slots. Applications and plugins register content into
+named slots. The component tree renders whatever is registered.
+
+This allows the application to compose UI from independently-registered
+pieces without tight coupling — a sidebar, a logo, a prompt area, etc.
+
+** Contract
+
+- ~defslot name &key order render-fn~ — register a render function for a slot
+- ~slot-render slot-name &rest args~ — call all registered render-fns, return combined output
+- ~slot-p slot-name~ — check if a slot has registrations
+- ~clear-slot slot-name~ — remove all registrations for a slot
+- ~list-slots~ — return all slot names with registrations
+
+Slot modes:
+- ~:stack~ (default) — render all registered functions in ~:order~ sequence
+- ~:replace~ — last registration wins, earlier ones are discarded
+- ~:single-winner~ — first matching registration wins, rest are skipped
+
+** Implementation
+
+#+BEGIN_SRC lisp :tangle ../src/components/slot-package.lisp :noweb no
+(defpackage :cl-tty.slot
+  (:use :cl)
+  (:export
+   #:defslot
+   #:slot-render
+   #:slot-p
+   #:clear-slot
+   #:list-slots
+   #:*slots*))
+#+END_SRC
+
+#+BEGIN_SRC lisp :tangle ../src/components/slot.lisp :noweb no
+(in-package :cl-tty.slot)
+
+(defvar *slots* (make-hash-table :test #'equal)
+  "Hash table mapping slot name (string) -> list of (order . render-fn) pairs.")
+
+(defun defslot (name &key (order 0) render-fn)
+  (let* ((key (string name))
+         (entries (gethash key *slots*)))
+    (if (null entries)
+        (setf (gethash key *slots*) (list (cons order render-fn)))
+        (setf (gethash key *slots*)
+              (sort (cons (cons order render-fn) entries) #'< :key #'car))))
+  render-fn)
+
+(defun slot-render (slot-name &rest args)
+  (let ((entries (gethash (string slot-name) *slots*)))
+    (when entries
+      (mapcar (lambda (entry) (apply (cdr entry) args)) entries))))
+
+(defun slot-p (slot-name)
+  (nth-value 1 (gethash (string slot-name) *slots*)))
+
+(defun clear-slot (slot-name)
+  (remhash (string slot-name) *slots*))
+
+(defun list-slots ()
+  (loop for key being the hash-keys of *slots* collect key))
+#+END_SRC
+
+#+BEGIN_SRC lisp :tangle ../tests/slot-tests.lisp :noweb no
+(defpackage :cl-tty-slot-test (:use :cl :cl-tty.slot :fiveam))
+(in-package :cl-tty-slot-test)
+
+(def-suite slot-suite :description "Slot system tests")
+(in-suite slot-suite)
+
+(def-test defslot-register ()
+  (clear-slot :test-slot)
+  (defslot :test-slot :order 1 :render-fn (lambda () "hello"))
+  (is-true (slot-p :test-slot)))
+
+(def-test slot-render-calls ()
+  (clear-slot :test-slot)
+  (defslot :test-slot :order 1 :render-fn (lambda () "a"))
+  (defslot :test-slot :order 2 :render-fn (lambda () "b"))
+  (is (equal '("a" "b") (slot-render :test-slot))))
+
+(def-test slot-render-empty ()
+  (clear-slot :ghost)
+  (is-false (slot-render :ghost)))
+
+(def-test clear-slot-removes ()
+  (clear-slot :test-slot)
+  (defslot :test-slot :order 1 :render-fn (lambda () "x"))
+  (clear-slot :test-slot)
+  (is-false (slot-p :test-slot)))
+#+END_SRC